The infestation of companion animals, and in particular household pets such as dogs and cats, with ectoparasites such as fleas, ticks and the like, which live by hematophagy (i.e., by sucking the animal's blood), is highly undesirable. The prior art has developed numerous ready-to-use topical formulations and compositions for treating such infestations, many of which are “spot on” or “pour on” formulations that are applied by deposition on the animal's skin, and which contain an N-phenyl pyrazole, and in particular, 1-[2,6-Cl2-4-CF3-phenyl]-3-CN-4-[SO—CF3]-5-NH2-pyrazole, whose common name is fipronil, as the active ingredient. Fipronil is an insecticide that is particularly effective to control and/or eliminate adult fleas and ticks, and when applied topically, is acceptably safe for use on companion animals such as dogs and cats.
U.S. Pat. No. 6,395,765 to Etchegaray, which is incorporated herein by reference in its entirety, discloses and claims particular ectoparasiticidal compositions comprising (a) an N-phenyl pyrazole, such as fipronil, as the active ingredient, along with inert, inactive ingredients including (b) a crystallization inhibitor, (c) an organic solvent, and (d) an organic co-solvent. A variety of specific crystallization inhibitors, organic solvents and organic co-solvents are disclosed.
In particular, the preferred crystallization inhibitor system is described as being a combination of a film-forming agent of polymer type and a surfactant, with the film-forming agent of polymer type being most preferably exemplified by polyvinylpyrrolidone, polyvinyl alcohols, and copolymers of vinyl acetate and vinylpyrrolidone, and with the surfactant being most preferably exemplified by polyoxyethylenated sorbitan esters, and in particular, polysorbate 80. It is believed that these crystallization inhibitors act by forming a film matrix which, while possibly allowing small crystals to form, inhibits their subsequent growth.
Although pesticidal compositions that include this type of crystallization inhibitor system are effective, it has been determined that the rate at which ectoparasites such as fleas are eradicated is not optimal and can be improved by utilizing a different class of crystallization inhibitors, particularly those which are not film-forming agents of polymer type.
It is therefore the principal object of the present invention to provide ectoparasiticidal formulations for the treatment and protection of companion animals having enhanced efficacy.
It is another object of the present invention to provide ectoparasiticidal compositions that are easy to use.
It is yet a further object of the present invention to provide ectoparasiticidal formulations having a higher rate of kill of parasites than can be achieved using presently-available compositions.